The present disclosure relates to a charging device that charges a surface of a photoreceptor to a predetermined charging potential and an image forming device including the charging device.
An electrophotographic image forming device, such as a copy machine, a printer, a facsimile device, a multifunction peripheral, or the like, includes a charging device that charges a surface of a photoreceptor to a predetermined charging potential in order to enable formation of an electrostatic latent image on the surface of the photoreceptor. As the charging device, there is a scorotron charging device including a discharge electrode that generates corona discharge between the photoreceptor and the discharge electrode and a grid electrode that is arranged between the discharge and the photoreceptor electrode.
Coincidently, a surface potential of the photoreceptor that has been charged by the charging device is required to be a potential suitable for development in a developing position in which an electrostatic latent image is developed by a developing device. On the other hand, the charging performance of the photoreceptor is influenced by change in layer thickness due to a shave of a photosensitive layer, which is generated by use of the photoreceptor, and change in temperature and humidity of a surrounding environment of the photoreceptor, and thus, varies. That is, in the scorotron charging device, in a state in which each of a discharge voltage that is applied to the discharge electrode and a grid voltage that is applied to the grid electrode is maintained constant, the surface potential of the photoreceptor varies in accordance with change in layer thickness of the photosensitive layer and change in temperature and humidity. Therefore, the surface potential of the photoreceptor cannot be maintained at a potential which is suitable for development.
As a technology that solves the above-described problem, a technology in which charging control of the charging device is performed in accordance with change in layer thickness of the photosensitive layer and change in temperature and humidity has been conventionally known. In the conventionally known technology, in a state in which a discharge voltage that is applied to the discharge electrode is maintained constant, a grid voltage that is applied to the grid electrode is controlled, based on a count value of the number of copies and detection values of a temperature and a humidity, which are parameters that correspond to change in layer thickness of the photosensitive layer.